Fire-resistant functional fluids

ABSTRACT

PRODUCTION OF FUNCTIONAL FLUIDS, PARTICULARLY AIRCRAFT HYDRAULIC FLUIDS, OF IMPROOVED FIRE RESISTANCE, COMPRISING A FUNCTIONAL FLUID BASE STOCK, SUCH AS A PHOSPHATE ESTER, E.G., DI-N-BUTYL PHENYL PHOSPHATE, OR MIXTURES OF SUCH BASE STOCKS, AND A SMALL AMOUNTS OF AN ARYL SELENIDE COMPOUNDS, PREFERABLY A CHLORINATED ARYL SELENIDE, E.G., ETHYL P-CHLORO PHENYL SELENIDE.

United States Patent 3,730,897 FIRE-RESISTANT FUNCTIONAL FLUIDS RobertS. McCord, Pacific Palisades, Donald H. Nail, Los Angeles, and Martin B.Sheratte, Reseda, Calif assignors to McDonnell Douglas Corporation,Santa Monica, Calif. No Drawing. Filed Mar. 29, 1971, Ser. No. 129,268Int. Cl. C09k 3/00 U.S. Cl. 252-78 25 Claims ABSTRACT OF THE DISCLOSUREProduction of functional fluids, particularly aircraft hydraulic fluids,of improved fire resistance, comprising a functional fluid Ibase stock,such as a phosphate ester, e.g., di-n-butyl phenyl phosphate, ormixtures of such base stocks, and a small amount of an aryl selenidecompound, preferably a chlorinated aryl selenide, e.g., ethyl p-chlorophenyl selenide.

This invention relates to functional fluid compositions having provedfire resistance and is particularly directed to compositions comprisingcertain functional fluids and an additive amount sufficient to improvefire resistance, of certain selenium compounds.

Many different types of materials are employed as functional fluids andfunctional fluids are utilized in a wide variety of applications. Thus,such fluids have been utilized as electronic coolants, diffusion pumpfluids, lubricants, damping fluid, power transmission and hydraulicfluids, heat transfer fluids and heat pump fluids. A particularlyimportant application of such functional fluids has been theirutilization as hydraulic fluids and lubricants in aircraft, requiringsuccessful operation of such fluids over a wide temperature range, aparticularly important and highly desirable property of such fluidsbeing fire resistant.

Functional and hydraulic fluids employed in many industrial applicationsand particularly hydraulic fluids for aircraft must meet a number ofimportant requirements. Thus, such hydraulic fluids particularly foraircraft use, should be operable over a wide temperature range, shouldhave good stability at relatively high temperatures and preferably havelubricating characteristics. In addition to having the usual combinationof properties making it a good lubricant or hydraulic fluid, such fluidshould also have relatively low viscosity at extremely low temperaturesand an adequately high viscosity at relatively high temperatures, andmust have adequate stability at the high operating temperature of use.Further, it is of importance that such fluids be compatible with and notadversely affect materials including metals and non-metals such aselastomeric seals of the system, in which the fluid is employed. It isparticularly important in aircraft hydraulic fluids and lubricants thatsuch fluids have as high a fire resistance as possible to preventignition if such fluids are accidentally or as result of damage to thehydraulic system, sprayed onto or into contact with surfaces ormaterials of high temperature.

While many functional and hydraulic fluid compositions have beendeveloped having most of the aforementioned required properties, many ofthese compositions do not have the requisite high fire resistancedesired particularly for use of such functional fluid or hydraulic fluidcompositions in modern high speed aircraft or in a hydraulic systemlocated near a high temperature jet-turbine power plant of a jet-turbineaircraft.

Thus, as an illustration, many functional and hydraulic fluids have anautoignition temperature ranging from about 450 to about 750 F. It isparticularly desirable to increase the autoignition temperature of suchfunctional and hydraulic fluids to the range of about 800 to about 1,000F.

It has now been found in accordance with the present invention that thefire resistance, or autoignition temperature, of functional fluid orhydraulic fluid compositions, can be significantly improved by theaddition to such compositions of a small amount of certain seleniumcompounds, in the form of certain aryl selenides and diselen-ides,especially chlorinated phenyl selenides and diselenides, defined ingreater detail hereinafter. The inclusion of such selenium additives infunctional and hydraulic fluid compositions generally does not adverselyaffect any of the above noted important characteristics of such fluids,particularly aircraft hydraulic fluids, including their desirableviscosity characteristics.

Another important feature is that certain recently developed hydraulicfluids for aircraft use have been designed particularly to have reduceddensity, but many of these low density fluids have inferior fireresistance to the higher densiity hydraulic fluids, and it has beenfound that selenium additives of the invention when incorporated intosuch low density fluids substantially increase the fire resistance andreduce the flammability of these low density hydraulic fluids.

The use of dialkyl selenides as oxidation inhibitors for orthosilicatefluids is described in U.S. Patent 3,118,841 to Moreton. In such patentthe selenide, e.g., dilauryl selenide, is employed in combination withother oxidation inhibitors such as phenyl alpha naphythylamine. However,selenides which inhibit oxidation in liquids do not necessarily functionto reduce flammability, or to increase autogenous ignition temperatureof a fluid, and in such patent only orthosilicates are employed as thebase stock. Further, many of the selenides are toxic, thermallyunstable, insufliciently soluble at the working temperature, or have anobjectionable odor. Certain selenides also tend to corrode metals.Moreover, in order to effectively reduce flammability, seleniumcompounds should also possess the property of decomposing in the plasmacondition in flames to prevent or poison continuation of the flame.

It has been found that the aryl selenides and particularly thechlorinated aryl selenides of the invention not only function tosubstantially increase autogenous ignition (autoignition) temperatureand reduce flammability of a wide variety of functional fluids andhydraulic fluids, but in addition have the advantageous properties ofbeing thermally stable, free from toxicity, relatively free fromcorrosion, do not have an objectionable odor, and have sufiicientsolubility in most functional and hydraulic fluids to effectivelyfunction as flame inhibitors. In addition, the aryl, particularly thechlorinated aryl, selenides employed according to the invention have noadverse effect on low temperature viscosity of the functional fluids,particularly when employed as hydraulic fluids in aircraft, do notadversely affect the thermal stability of the fluid, and are ofrelatively low cost.

Effective selenium compounds, that is aryl selenides, for use asadditives in functional and hydraulic fluids to reduce flammability andincrease autoignition temperature of the fluid, according to theinvention, have the formula ArSeR, where Ar is a member selected fromthe group consisting of aryl and substituted aryl including asubstituent selected from the group consisting of alkyl, halogen,alkoxy, aryloxy, amino and dialkylarnino, and R is a member selectedfrom the group consisting of unsubstituted and substituted alkyl, aryland aryloxy, including a substituent selected from the group consistingof halogen, amino and diakylamino; and SeAr, where Ar has the samedefinition as Ar above, and Ar and Ar are the same or different.

Thus, Ar and Ar can be phenyl, naphthyl anthranyl, and the like, andsuch aryl groups can contain alkyl substituents, such as methyl, ethyl,propyl, butyl, and branched chain alkyls such as isopropyl and isobutyl,and the like, halogen atoms such as chlorine and bromine, alkoxy such asmethoxy, ethoxy, propoxy, and the like, aryloxy such as phenoxy andnaphthoxy, amino and dialkylamino such as dimethylamino, diethylamino,and the like, such alkyl groups containing from 1 to about carbon atoms.R can be alkyl such as methyl, ethyl, propyl, isopropyl, butyl,isobutyl, and the like, of from 1 to about 10 carbon atoms, aryl such asphenyl, naphthyl, and the like, aryloxy such as phenoxy and naphthoxy,and substituted alkyl, aryl and aryloxy radicals containing substituentssuch as halogen, e.g., chlorine and bromine, amino and dialkylamino suchas dimethylamino and diethylamino, and the like, such alkyl groupscontaining from 1 to about 10 carbon atoms.

The preferred aryl selenides according to the invention are thoseselected from the group having the general formulae:

SeR

e-Se

where X is selected from the group consisting of H, alkyl, both straightchain and branched chain and having 1 to about 10 carbon atoms, such asmethyl, ethyl, propyl, butyl, isopropyl, pentyl, and the like, halogensuch as chlorine and bromine, alkoxy such as methoxy, ethoxy, propoxy,isopropoxy, butoxy, isobutoxy, amino and dialkylamino such asdimethylamino, diethylamino, and the like, and R is alkyl of from about1 to about 12 carbon atoms, both straight and branched chain, such asmethyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, andthe like.

Compounds which have been found particularly effective according to theinvention are the halogenated, e.g., chlorinated or brominated arylselenides, especially the chlorinated aryl selenides, that is, selenidesof the formulae noted immediately above, where X is halogen such aschlorine. The aryl nuclei of the above noted formulae each can containone or more of the X, e.g., chloro or bromo, substituents, such as one,two or three such halogen, e.g., chlorine, atoms on each of the phenylnuclei. The most desirable chlorinated selenides of these types havebeen found to be ethyl p-chlorophenyl selenide and 4,4-dichlorodiphenyldiselenide. Other exemplary chlororinated aryl selenides having astructure as defined by the above formulae include methyl p-chlorophenylselenide, ethyl and propyl o-chlorophenyl selenides, methyl and ethyl2,4-dichlorophenyl selenides, ethyl 2,4,6- trichlorophenyl selenide,2,2'-dichlorodiphenyl diselenide, 2,4,2',4'-tetrachloro diphenyldiselenide and 2,4,6,2,4', 6-hexachloro diphenyl diselenide. Brominatedanalogues corresponding to the above specific examples of thechlorinated selenides and diselenides can be employed.

The following base stocks are illustrative of typical base stocks thatcan be utilized in preparing the functional fluid compositions of thepresent invention, and the instant invention can be practiced utilizingthe various modifications of the base stocks which are set forth below.

Preferably functional fluid base stocks are employed which are selectedfrom the group consisting of phosphorus esters, amides of an acid ofphosphorus, diand tricarboxylic acid esters, and petroleum hydrocarbons.

Phosphorus esters which can be employed according to the invention havethe general formula:

Rt-O.

R20m-P=0 Rr-O 4 where s, m and n can be 0 or 1, and not more than two ofs, m, and n can be 0, where R R and R each can be aryl such as phenyland naphthyl, alkaryl such as cresyl, xylyl, ethyl phenyl, propylphenyl, isopropyl phenyl, and the like, said aryl and alkaryl radicalspreferably containing from 6 to about 8 carbon atoms, alkyl, bothstraight chain and branched chain of from about 3 to about 10 carbonatoms such as n-propyl, n-butyl, namyl, n-hexyl, isopropyl, isobutyl,and the like, and alkoxyalkyl having from about 3 to about 8 carbonatoms such as methoxy methyl, methoxy ethyl, ethoxy ethyl, methoxypropyl, and the like.

The corresponding phosphonates can also be employed, where one of s, mand n is 0, and the corresponding phosphinates where two of s, m and nare 0.

Preferred phosphorus esters are the dialkyl aryl, triaryl, trialkyl andalkyl diaryl phosphates.

Examples of such phosphate esters are the dialkyl aryl phosphates inwhich the alkyl groups are either straight chain or branched chain andcontain from about 3 to about 10 carbon atoms, such as n-propyl,n-butyl, n-amyl, n-hexyl, isopropyl, isobutyl, isoamyl, and the arylradicals have from 6 to 8 carbon atoms and can be phenyl, cresyl orxylyl, particularly dialkyl phenyl phosphates including dibutyl phenylphosphate, butyl amyl phenyl phosphate, butyl hexyl phenyl phosphate,butyl heptyl phenyl phosphate, butyl octyl phenyl phosphate, diamylphenyl phosphate, amyl hexyl phenyl phosphate, amyl heptyl phenylphosphate, and dihexyl phenyl phosphate.

Examples of triaryl phosphates to which the aryl selenides, especiallychlorinated selenides of the invention can be added are those in whichthe aryl radicals of such phosphates have from 6 to 8 carbon atoms, thatis, may be phenyl, cresyl or xylyl, and in which the total number ofcarbon atoms in all three of the aryl radicals is from 19 to 24, thatis, in which the three radicals include at least one cresyl or xylylradical. Examples of such phosphates include tricresyl, trixylyl, phenyldicresyl, and cresyl diphenyl phosphates.

Examples of trialkyl phosphates employed according to the inventioninclude phosphates having alkyl groups which are either straight chainor branched chain with from about 3 to about 10 carbon atoms, such asn-propyl n-butyl, n-amyl and n-hexyl, particularly tri-n-butylphosphate, tri(2-ethyl hexyl) phosphate and triisononyl phosphate, thestraight chain alkyl groups preferably containing from 4 to 6 carbonatoms.

Examples of alkyl diaryl phosphates which can be employed to produce theinvention compositions include those in which the aryl radicals of suchphosphates may have from 6 to 8 carbon atoms and may be phenyl, cresylor xylyl, and the alkyl radical may have from about 3 to about 10 carbonatoms, examples of which are given above. Examples of the alkyl diarylphosphates include butyl diphenyl, amyl diphenyl, hexyl diphenyl, heptyldiphenyl, octyl diphenyl, 6-methyl heptyl diphenyl, 2-ethylhexyldiphenyl, butyl phenyl cresyl, amyl phenyl xylyl, and butyl dicresylphosphates.

Functional fluid base stocks according to the invention also includephosphonate and phosphinate esters having alkyl and aryl groupscorresponding to thoese defined above with respect to the phopshateesters.

Examples of phosphinate esters to which the invention principles areapplicable include phenyl-di-n-propyl phosphinate, phenyl-di-n-butylphosphinate, phenyl-di-n-pent yl phosphinate, p-methoxyphenyl-di-n-butylphosphinate, tert-butylphenyl-di n butyl phosphinate. Examples ofphosphonate esters to which the invention is applicable includealiphatic phosphonates such as alkyl alkenyl phosphonate, e.g., dioctylisooctene phosphonate, an alkyl alkane phosphonate such as di-n-butyln-octane phosphonate, di-isooctyl pentane phosphonate, and dimethyldecane phosphonate, a mixed alkl aryl phosphonate, for example, di-octylphenyl phopshonate, di(n-amyl) phenyl phosphonate, di(n-butyl) phenylphosphonate, phenyl butyl hexane phosphonate and butyl bis-benzenephosphonate.

Another class of phosphorus-containing compounds in which the selenidesof the invention can be employed as additives are the amides of acids ofphosphorus, e.g., amido phosphates, including the mono-, diand triamidesof an acid of phosphorus, an example of which is phenyl N-methylN-n-butyl-N-methyl-N'-n-butyl phosphoro-diamidate. Additional examplesare m-cresyl-p-cresyl-N,N- dimethylphosphoroamidate, di-m-cresyl |N,Ndimethylphosphoroamidate, di-p-cresyl N,N dimethylphosphoroamidate,phenyl-N,N-dimethyl-N',N'-dimetliylphosphorodiamidate, Nmethyl-N-butyl-N',N"-tetramethylphosphorotriamidate,N,N'-di-n-propyl-N"-dimethylphosphorotriarnidate.

Another class of functional fluid base stocks whose antoignitiontemperature can be improved by incorporation of the aryl selenides,particularly the chlorinated aryl selenides of the invention are thediand tricarboxylic acid esters, particularly the dicarboxylic acidesters. Preferred types of the latter compounds are the alkyl diestersof adipic and sebacic acid, that is the diester adipates and sebacates.Such esters can contain alkyl groups, either straight chain or branchedchain, containing from about 4 to about 12 carbon atoms including butyl,isobutyl, amyl, pentyl, hexyl, isohexyl, nonyl, decyl and isodecylgroups. Specific examples of these base stocks are dihexyl, diZ-ethylhexyl, dioctyl, dinonyl, didecyl and diisodecyl adipate, and thecorresponding sebacates. Also, the diesters of the dicarboxylic aromaticacids, particularly the diesters of phthalic acid, that is the phthalatediesters can be employed as base stocks. The diesters of such acids cancontain alkyl groups of from 4 to 12 carbon atoms, examples of which aregiven above with respect to the diesters of the dicarboxylic aliphaticacids, adipic and sebacic acid. Illustrative examples of the diesterphthalates which can be employed are di-n-butyl phthalate, dihexylphthalate, dioctyl phthalate, dinon'yl phthalate, didecyl phthalate, anddiisodecyl phthalate.

There can also be employed as functional fluid base stocks according tothe invention the esters of tricarboxylic acids, particularly thearomatic tricarboxylic acids such as trimellitic acid. The triesters ofsuch acids can contain alkyl groups of from 4 to 2 carbon atoms,illustrative examples of which are noted above with respect to thedialkyl esters of phthalic acid, specific examples of trimellitatetriesters including tri-butyl, tIi-hexyl, trioctyl, tri-isooctyl,tri-nonyl, tri-decyl and tri-isodecyl trimellitate.

There can also be employed as functional fluid base stocks to which thearyl selenides are added according to the invention, petroleumhydrocarbons, which can contain carbon chains of from C to about Ccarbon atoms. A typical example of such a petroleum hydrocarbon is thered petroleum hydrocarbon liquid according to military specificationMILH-5606B, understood to contain carbon chains of about C to about Ccarbon atoms, generally employed as a hydraulic fluid in militaryaircraft.

It is also contemplated within the scope of the present invention thatmixtures of individual functional or hydraulic fluid components areincluded to form a single base stock. Thus, for example blends of estersof an acid of phosphorus can be employed, e.g., a blend of tri-nbutylphosphate and tricresyl phosphate, blends of an ester of an acid ofphosphorus and a dicarboxylic acid diester such as the aliphaticdiesters of adipic, sebacic or phthalic acid, e.g., a mixture oftri-n-butyl phosphate and di-isodecyl adipate and/or diisodecylphthalate, or a combination or blend of dicarboxylic acid diesters and/or tricarboxylic acid triesters can be employed, such as a blend ofdi-isodecyl adipate and di-isodecyl phthalate.

Thus, there can be employed as functional fluid base stocks a blend ormixture of a phosphorus ester such as a phosphate and an alkyl diesterof phthalic acid, with or without an alkyl diester of adipic acid and/orof sebacic acid, wherein said alkyl groups contain from about 4 to about12 carbon atoms as described and claimed in the copending applicationFunctional Fluid Compositions, M. B. Sheratte, Ser. No. 129,270, filedMar. 29, 1971. In addition, functional fluid base stocks can be utilizedcomprising a blend or mixture of a phosphorus ester such as a phosphateand an alkyl diester of adipic acid and /or of sebacic acid, as definedabove, and as described and claimed in the copending application,Functional Fluids, M. B. Sheratte, Ser. No. 129,269, filed Mar. 29,1971.

The functional or hydraulic fluid base stocks employed and describedabove, can also contain other additives such as viscosity indeximprovers, in a small amount ranging from 0 to about 10%, generallyabout 2 to about 10%, by weight of the composition. Examples of thelatter are polyal kyl acrylates and methacrylates, the polyalkylmethacr'ylates generally being preferred, and in which the alkyl groupsmay contain from about 4 to about 12 carbon atoms, either straight orbranched chain. Specific examples of such viscosity index improvers arepolybutyl methacrylate and poly n-hexyl acrylate, having an averagemolecular weight between about 6,000 and about 12,000. Other additivessuch as corrosion inhibitors, stabilizers, metal deactivators, and thelike, can also be employed.

For greatest effectiveness in substantially reducing the flammability,and for correspondingly substantially increasing the autoignitiontemperature of the above functional fluid base stocks according to theinvention, it is usually desirable to employ only a small amount of thearyl selenide or halogenated aryl selenide in the functional orhydraulic fluid base stock. Generally, there can be employed as littleas 0.25% and up to about 5% of the selenide additive of the invention,preferably from about 0.5 to about 2% of such selenide, in thefunctional fluid base stock, based on the weight of the composition. Ithas been found that an optimum amount of such selenide additive rangesfrom about 0.8 to about 2% by weight of the composition.

The following are examples of preparation of two of the preferredchlorinated selenide additives of the invention, such examples beingsimply exemplary of the preparation generally of the aryl selenidesemployed as additives according to the invention:

EXAMPLE 1 Preparation of 4,4-dichlorodiphenyl diselenide Magnesium (24.0g., 1.0 mole) was placed in a 2000 ml. flask, which was equipped with areflux condensor, stirrer, thermometer, liquid addition funnel, poweraddition funnel and a nitrogen inlet and outlet. Selenium powder (87 g.,1.1 mole) was placed in the powder addition funnel, and the entireapparatus was evacuated for several hours to remove traces of water. Theapparatus was then filled and flushed with dry nitrogen.

A solution of p-dichlorobenzene (147 g., 1.0 mole) in tetrahydrofurane(300 ml.) was placed in the liquid addition funnel. 7

Approximately 1 ml. of ethylene dichloride was added to the flask toactivate the magnesium, and then about 20 ml. of the p-dichlorobenzenesolution was run in. The reaction generally started within 10-20 minutesand the vigorous exotherm took the temperature to 90 C. When the initialvigorous reaction had subsided, the rest of the p-dichlorobenzenesolution was added at a rate which maintained the temperature at 6585 C.When all the dichlorobenzene had been added, the mixture was heatedunder reflux for an hour, forming the intermediate reaction product,p-chlorophenyl magnesium chloride.

The temperature was then allowed to fall to about 65 0., and theselenium powder was added carefully so that the temperature of themixture remained below 80 C.

After all the selenium had been added, the mixture was again heatedunder reflux for 1 hour, forming p-chlorophenyl selenium magnesiumchloride. After cooling, the resultant mixture was cautiously pouredover a mixture of 300 ml. concentrated hydrochloric acid and 500 g. ice.Air was bubbled through the resultant mixture for 20 hours, after whichthe selenium-containing product, 4,4- dichlorodiphenyl diselenide, wasobtained as a greenish stilf paste. The aqueous layer was decanted, andthe green paste was dissolved in tetrahydrofurane. The product wasfiltered from excess selenium powder, which was recovered. The filtratewas evaporated to dryness, and the solid orange product was washed oncewith methanol. After drying, the product was a yellow to orange powder,which weighed 133 g., corresponding to a 70% yield. The theoreticalyield is 190.5 g.

EXAMPLE 2 Preparation of ethyl p-chlorophenyl selenide A solution ofp-chlorophenyl selenium magnesium chloride was prepared as described inExample 1 above, and dissolved in 60 ml. tetrahydrofurane. To thissolution was slowly added 0.2 mole of ethyl chloride. After theexothermic reaction had stopped, the reaction mixture was heated underreflux for 1 hour. The mixture of products was dissolved in ether,washed several times with water, dried over sodium sulphate, andfractionally distilled. In addition to an approximately 60% yield ofethyl p-chlorophenyl selenide, approximately 25% of4,4'-dichlorodiphenyl selenide and 10% of 4,4'-dichlorodiphenyldiselenide were also obtained.

The following are examples illustrating practice of the invention byincorporation of aryl selenide additives according to the invention intofunctional fluid base stocks. In the examples below the term AIT meansautoignition temperature, the autoignition temperature of the functionalfluid compositions of the invention according to the examples belowbeing determined in accordance with standard method of test forautoignition temperature in accordance with ASTM D 2155 procedure.

EXAMPLE 3 TABLE 1 Additive coneentra- AIT Additive tion, percent F.)

4,4'-dichlorodiphenyldiselenide 740 d 0. 3 875 0. 6 910 0.9 930 FromTable 1 above it is seen that incorporation of only 0.3% by weight ofthe chlorinated selenide additive increases AIT of the control fluid Afrom an AIT of 740 F. to 875 F., and that increased proportions of thechlorinated selenide additive to 0.9% increases AIT further to 930 F.,almost 200 F. higher than the 740 F. AIT of the control fluid.

EXAMPLE 4 To the functional fluid blend A of Example 3 is added ethylp-chlorophenyl selenide in an amount of 0.6% by weight of thecomposition, and the AIT of the resulting composition is determinedagainst the control fluid A containing no selenide additive. The resultsare shown in Table 2 below:

TABLE 2 Additive concentra- AIT Additive tion, percent F.)

Fluid:

A Ethyl p-chlorophenyl selenide 0 740 A do 0. 6 930 From Table 2 above,it is seen that the addition of 0.6% of the chlorinated additive of thisexample increases the AIT of 740 F. for the control containing noselenide additive, to 930 F.

EXAMPLE 5 TABLE 3 Additive coneentra- AIT Additive tion, percent F.)

Fluid:

B Ethyl p-chlorophenyl selenide. O 700 B .do 0. 6 850 From the Table 3above it is seen that the AIT of the invention composition containingthe chlorinated selenide is increased from an AIT of less than 700 F.for the control, to 850 F.

EXAMPLE 6 Ethyl p-chlorophenyl selenide is added to a red petroleumhydrocarbon liquid containing hydrocarbon chains ranging from C to C(MIL-H-5606B), designated C in the table below, in an amount of 0.6% byweight of the total composition, and the AIT of the resultingcomposition, determined against a control of the same petroleumhydrocarbon liquid but in the absence of any additive selenide. Theresults are shown in Table 4 below:

TAB LE 4 Additive concentra- AIT Additive tion, percent F.)

Fluid:

C Ethyl p-chlorophenyl selenide- 0 470 C do 0. 6 590 It is noted fromTable 4 above that the AIT of the control composition C of 470 F., isincreased to 590 F. by the incorporation of the chlorinated selenidenoted above in an amount of 0.6% by weight.

EXAMPLE 7 Phenyl ethyl selenide is added to tri-n-butyl phosphate in anamount of 0.5% by weight of the composition, and the resultingcomposition D tested for AIT against a control of tri-n-butyl phosphatecontaining no selenide.

The control has an AIT of 730 F. and the blend containing the abovephenyl ethyl selenide in an amount of 0.5 has a substantially higher AITof 915 F.

EXAMPLE 8 To the functional fluid blend A of Example 3 above, is added4,4-di(seleno ethyl)diphenyl ether, in an amount of 0.6% by weight ofthe total composition. The composition containing the selenide additiveis tested for AIT against a control of fluid A in the absence of anyselenide.

The resulting composition containing the above selenide has an AIT of900 F. against an AIT of only 740 F. for the control rfluid A.

EXAMPLE 9 To a blend of a functional fluid containing 50% diisodecyladipate, 30% tri-n-butyl phosphate and 20% dibutyl phenyl phosphate, byweight, designated composition E, is added 4,4'-dichlorodiphenyldiselenide, in an amount of 0.9% by weight of the composition, and thehot manifold temperature of the resulting composition containing thechlorinated selenide is obtained against the control composition Econtaining no selenide.

Hot manifold temperature is obtained by a standard procedure, FederalTest Standard 791, method 6053, and varying the manifold temperature tonote the maximum temperature of non-ignition.

The hot manifold temperature of the control composition E is 1,070 F.,whereas the hot manifold temperature of the same functional fluid blendE containing the 0.9% of the above chlorinated diselenide is 1,240 F.

EXAMPLE 10 To a blend of a functional fluid containing 50% diisodecyladipate, 40% tri-n-butyl phosphate, and 10% triisodecyl-tri-mellitate,designated composition F, is added ethyl p-chlorophenyl selenide in anamount of 0.9% by weight, and the AIT of the resulting composition isobtained against the control composition F in the absence of anyselenide.

The AIT of the control composition F is only 630 F., whereas compositionF containing the above chlorinated selenide has a substantially higherAIT of 850 F.

EXAMPLE 11 To a functional fluid blend containing 39% tri-n-butylphosphate, 47% di-isodecyl adipate, and 10% di-isodecyl phthalate, andcontaining minor amounts of oxidation inhibitor, designated compositionG, and to another functional fluid blend containing 56% tri-n-butylphosphate, 35% di-isodecyl adipate, 5% poly-n-hexyl acrylate having anaverage molecular weight of about 12,000 as viscosity index improver,and a small amount of oxidation inhibitor additive, designatedcomposition H, is added 4,4- dichlorodiphenyl diselenide in each case inan amount of 0.8% by weight of each of the blends.

The AIT of each of the above compositions G and H containing thechlorinated aryl selenide, and the AIT of the corresponding controls,compositions G and H, each in the absence of any selenide, are obtained,and the results noted in Table 5 below:

TAB LE 5 Additive concentra- AIT Additive tion, percent F.)

From Table above, it is seen that the AIT of each of the controls,compositions G and H, in the absence of any selenide is 600 F., and suchAIT was substantially increased to 870 F. and to 895 F. for compositionsG and H containing the 0.8% of the chlorinated selenide, respectively.

In each of the Examples 3 to 11 above, a substantial improvement inautoignition temperature, and corresponding reduction in flammability isobtained, by incorporating the aryl selenides of the invention into thevarious functional fluids and blends thereof set forth in the examples,and such reduction in flammability is obtained without reducing the hightemperature thermal stability of the functional fluid and without anyincrease in low temperature viscosity of the fluid, employing selected10 selenium compounds having relatively good solubility in such fluidsand hence high effectiveness therein, and which are free from toxicityand relatively odor-free.

From the foregoing, it is seen that the invention provides novelfunctional fluid compositions containing certain organo-seleniumcompounds which function efficiently as flame retardants or flameinhibitors in such fluids.

While we have described particular embodiments of our invention forpurposes of illustration, it will be understood that various changes andmodifications within the spirit of the invention can be made, and theinvention is not to be taken as limited except by the scope of theappended claims.

We claim:

1. A functional fluid composition consisting essentially of a majorportion of a functional fluid base stock selected from the groupconsisting of phosphorus esters, amides of an acid of phosphorus, diandtricarboxylic acid esters, and petroleum hydrocarbons containing carbonchains of from C to about C carbon atoms, and about 0.25 to about 5% byweight of a selenium compound having the general formulae:

SeR -Se-Se X and X X Wher X is halogen and R is alkyl of from about 1 toabout 12 carbon atoms.

2. A composition as defined in claim 1, wherein said selenium compoundhas the general formula:

SeR

where X is halogen and R is alkyl of from about 1 to about 12 carbonatoms, there being from 1 to 3 X substituents on the phenyl nucleus.

3. A composition as defined in claim 1, where said selenium compound hasthe general formula:

where X is halogen, there being from 1 to 3 X substituents on eachphenyl nucleus.

4. A composition as defined in claim 1, wherein said base stock is aphosphorus ester having the general formula:

where s, m and n are each an integer of 0 to 1, and not more than two ofs, m and n are 0, R R and R are each a member selected from the groupconsisting of aryl, alkaryl, alkyl of from about 3 to about 10 carbonatoms, and alkoxyalkyl having from about 3 to about 8 carbon atoms.

5. A composition as defined in claim 4, wherein s, m and n are each 1,and said phosphorus ester is a phosphate ester, and said seleniumcompound being present in an amount ranging from about 0.5 to about 2%by weight of said composition.

6. A composition as defined in claim 1, said base stock comprising apetroleum hydrocarbon containing carbon chains of from C to about Ccarbon atoms, and said selenium compound being a member selected fromthe group consisting of ethyl p-chlorophenyl selenide and4,4'-dichlorodiphenyl diselenide.

7. A functional fluid composition consisting essentially of a majorportion of a functional fluid base stock which 80B S Kg and X X where Xis halogen and R is alkyl of from about 1 to about 12 carbon atoms.

8. A composition as defined in claim 7, wherein said selenium compoundis present in an amount ranging from about 0.5 to about 2% by weight ofsaid composition.

9. A composition as defined in claim 7, wherein said base stockcomprises a mixture of a phosphate ester selected from the groupconsisting of dialkyl aryl, triaryl, trialkyl and alkyl diarylphosphates, and a dicarboxylic acid ester.

10. A composition as defined in claim 9, wherein said dicarboxylic acidester is selected from the group consisting of the alkyl diesters ofadipic and sebacic acid, containing alkyl groups of from about 4 toabout 12 carbon atoms.

11. A composition as defined in claim 9, wherein said dicarboxylic acidester is an alkyl diester of phthalic acid containing alkyl groups offrom about 4 to about 12 carbon atoms.

12. A composition as defined in claim 11, wherein said mixture includesa dicarboxylic acid ester selected from the group consisting of thealkyl diesters of adipic and sebacic acid, containing alkyl groups offrom about 4 to about 12 carbon atoms.

13. A composition as defined in claim 7, wherein said base stockcomprises a phosphate ester selected from the group consisting ofdialkyl aryl, triaryl, trialkyl and alkyl diaryl phosphates, and saidselenium compound is a member selected from the group consisting ofethyl p-chlorophenyl selenide and 4,4'-dichlorodiphenyl diselenide.

14. A composition as defined in claim 13, said selenium compound beingpresent in an amount ranging from about 0.25 to about 2% by weight ofsaid composition.

'15. A composition as defined in claim 7, wherein said base stockcomprises a mixture of a phosphate ester selected from the groupconsisting of dialkyl aryl, triaryl, trialkyl and alkyl diarylphosphates and a dicarboxylic acid diester selected from the groupconsisting of the alkyl diesters of adipic and sebacic acid, containingalkyl groups of from about 4 to about -12 carbon atoms, and saidselenium compound is a member selected from the group consisting ofethyl p-chlorophenyl selenide and 4,4-dichlorodiphenyl diselenide.

'16. A composition as defined in claim 7, said base stock comprising amixture of a phosphate ester selected from the group consisting ofdialkyl aryl, triaryl, trialkyl, and alkyl diaryl phosphates, and analkyl diester of phthalic acid containing alkyl groups of from about 4to about 12 carbon atoms, and said selenium compound being a memberselected from the group consisting of ethyl 12 p-chlorophenyl selenideand 4,4-dichlorodiphenyl diselenide.

17. A composition as defined in claim 16, wherein said mixture includesa dicarboxylic acid ester selected from the group consisting of thealkyl diesters of adipic and sebacic acid, containing alkyl groups offrom about 4 to about 12 carbon atoms.

'18. A composition as defined in claim 7, said base stock comprising amember selected from the group consisting of di-n-butyl phenylphosphate, tri-n-butyl phosphate an d tricresyl phosphate, and mixturesthereof, and said selenium compound is a member selected from the groupconsisting of ethyl p-chlorophenyl selenide, and 4,4'-dichlorodiphenyldiselenide, said selenium compound being present in an amount rangingfrom about 0.5 to about 2% by weight of said composition.

19. A composition as defined in claim 18, said base stock comprising amixture of tri-n-butyl phosphate and tricresyl phosphate.

20. A composition as defined in claim 18, said base stock including amember selected from the group consisting of diisodecyl adipate anddiisodecyl phthalate, and mixtures thereof.

21. A composition as defined in claim 18, said base stock including amixture of di-isodecyl phthalate and diisodecyl adipate.

22. A composition as defined in claim 18, said base stock being amixture of tri-n-butyl phosphate, diisodecyl adipate and diisodecylphthalate.

23. A composition as defined in claim 20, said base stock comprising amixture of tri-n-butyl phosphate, di-nbutyl phenyl phosphate anddiisodecyl adipate.

24. A composition as defined in claim 1, wherein said base stockcomprises a mixture of a dialkyl phthalate and a member selected fromthe group consisting of a dialkyl adipate and a dialkyl sebacate, andsaid selenium compound is a member selected from the group consisting ofethyl p-chlorophenyl selenide and 4,4-dichlorodiphenyl diselenide.

25. The composition as defined in claim 6, said petroleum hydrocarboncontaining carbon chains of from C to about C and said selenium compoundbeing present in an amount ranging from about 0.5 to about 2% by weightof said composition.

References Cited UNITED STATES PATENTS 6/ 1949 Denison et al 252-451/1961 Bolt et a1. 252-45 X OTHER REFERENCES MAYER WEIN'BLATT, PrimaryExaminer H. A. PITLICK, Assistant Examiner US. Cl. X.R.

